DE102011102597A1 - Thermally activated active material actuator i.e. shape memory alloy actuator, has heat sink that presents thermal conductivity rate greater than ambient rate and engages with active material element to present shorter cooling period - Google Patents

Abstract

The actuator has an thermally activated active material element (12) e.g. shape memory alloy (SMA) wire, to undergo reversible change in fundamental property when exposed to or occluded from a thermal activation signal to activate/deactivate the element for heating and cooling purpose. The element presents a cooling ambient rate when occluded from the signal after being activated, and a cooling period. A heat sink (14) presents a thermal conductivity rate greater than the ambient rate, and autonomously engages with the element when the element is activated to present shorter cooling period.

Description

Related applications

This patent application claims utility and in part proceeds from US Patent Application No. 12 / 437,768 entitled "Controlling Heat Transfer to Active Material Actuators Using Heat Sinks", filed May 8, 2009, and US Patent Application Ser No. 12/250 148, entitled "Active Material Elements Having Reinforced Structural Connectors," filed Oct. 13, 2008, the disclosures of which are incorporated herein by reference.

Background of the invention

1. Field of the invention

The present disclosure relates generally to arrangements for and methods for accelerating cooling in thermally activated active material actuators and, more particularly, to arrangements and methods for accelerating cooling within such actuators using both permanently and selectively engaged heat sinks.

2. Explanation of the prior art

Thermally activated actuators with an active material such. B. shape memory alloy (SMA) wires in the martensite state are activated by heating the material above an activation temperature. With respect to SMA wires, this generally causes the material to undergo phase transformation to austenite and contract in a manner that can be used to do work. Once activated, the actuator must experience a relatively long cooling period in which the temperature is lowered to a point below its transition temperature before being reactivated. During this period, the actuator is not available to do work so that the duration of the cool down period contributes significantly to the overall bandwidth of the actuator. It follows, therefore, that the shortening of the determining cooling period significantly reduces the bandwidth.

Conventional methods of cooling, however, which merely involve exposure of the material to ambient conditions, are often insufficient to achieve these goals and / or involve complex peripheral systems such as e.g. For example, forced air convection, etc. These problems arise specifically in the performance of actuators with an active material that must be subjected to rapid successive activations and / or effect actuation with fast reset (eg, <1 sec). As such, the long-felt desire in the art remains for an efficient arrangement and method for improving bandwidth by shortening the cooling period.

Brief summary of the invention

The present invention addresses the aforementioned problems by providing a new actuator with an active material that uses a heat sink to accelerate cooling over a thermal activation cycle. As such, the invention is useful to, among other things, reduce bandwidth and therefore improve actuator performance without the need for an additional source of cooling gas or liquid. The invention is also useful to reduce the likelihood of overheating during a thermal activation cycle, which provides for more efficient operation, and protects the integrity of the SMA actuator and / or device powered thereby.

In a first aspect of the invention, a thermally activated actuator having an active material is adapted to increase a bandwidth, and includes an active material actuator element and a heat sink. The element is operable to undergo a reversible change in a fundamental characteristic when exposed to or shielded from a thermal activation signal so as to heat and activate the element or allow the element to be cooled or deactivated. The element has an ambient cooling rate when it is shielded from the signal after it has been activated and a first cooling period based on the ambient rate. The heat sink has a rate of thermal conductivity higher than the ambient rate and automatically engages the element when the element is activated so as to have a second cooling period that is shorter than what would otherwise be provided by the first period would.

The disclosure which includes the use of an active material auxiliary member, a drive mechanism further comprising a pivot arm and rack gear and / or flexible curved structures to drive the heat sink, and a heat sink defining grooves, coolant openings and / or channels Having ribs included to further accelerate cooling is more readily understood by reference to the following detailed description of the various features of the disclosure and the examples contained therein.

Brief description of the different views of the drawing

A preferred embodiment (s) of the invention is (are) described below in detail with reference to the accompanying drawing FIG. described with exemplary scale, in which:

1a a cross-section of an actuator with an active material comprising a plurality of shape memory alloy wires and a heat sink having a first and a second part fitted together, and pluralities of grooves in which wires are arranged and defining ribs according to a preferred embodiment of the invention ;

1b a cross section of an inverted part, the in 1a wherein the grooves are omitted and a plurality of wires are retained and spaced within the channels defined by the ribs, in accordance with a preferred embodiment of the invention;

1c a cross-section of a plurality of wires forming rows and a sink having a plurality of sets of stackable mated parts, each set strengthening a row, according to a preferred embodiment of the invention;

2 a cross section of a plurality of wires and a sink defining a horizontal rib, according to a preferred embodiment of the invention;

3a 10 is an elevational view of a wire actuator and a heat sink having first and second inwardly curved, opposing, and flexible structures joined together by end caps in a deactivated / disengaged state (dashed lines) and an activated / engaged state, according to a preferred embodiment the invention is;

3b an outline of the in 3a and a first / s and a second opposite heat transfer mass / cooling pad associated with the structures and configured to increase the surface area of the sink according to a preferred embodiment of the invention is;

4a an elevation of a wire and a heat sink with a spring-loaded pivot arm, which is drivingly coupled to the wire and the heat transfer mass shown in a normal configuration in which the actuating wire is deactivated, according to a preferred embodiment of the invention;

4b an elevation of the actuating wire and the heat sink is in 4a with the wire beginning to be converted and actuated, the swing arm caused to pivot, and the sink being made to engage the wire;

4c an outline of the wire and the sink is in the 4a , b, wherein the wire has completed the conversion and actuation;

4d is a partial cross-sectional view of the pivot arm and the wire, which in the 4a -C are shown, and further illustrates a collar that directly couples the arm and the wire;

5 an elevation of an actuating wire, a heat sink defining a plurality of coolant channels, and a drive mechanism comprising a rack gear and a counterweight, according to a preferred embodiment of the invention;

6 an elevation of an actuating wire and a heat sink, which are drivingly coupled to an auxiliary wire and a spring-loaded pivot arm, wherein the actuator and the auxiliary wires are connected in series, according to a preferred embodiment of the invention;

7a an elevation of an actuating wire and a heat sink, which are drivingly coupled to an auxiliary wire and a spring-loaded pivot arm, wherein the actuator and the auxiliary wires are connected in parallel, according to a preferred embodiment of the invention; and

7b an elevation of the actuating wire and the heat sink, in 7a wherein the actuator and the auxiliary wires have been sequentially activated according to a preferred embodiment of the invention.

Detailed description of the invention

In general, the present invention relates to a new actuator 10 , which is a thermally activated element 12 made of an active material such. At least one shape memory alloy (SMA) wire and a heat sink 14 in functional contact with the element 12 includes ( 1a - 7b ). The actuator 10 has a bandwidth defined by a cycle that includes warm-up, cool-down, and deactivation periods. Both permanently and selectively engaged heat sink configurations are contemplated by the present invention. The heat sink 14 serves to shorten the cooling period and in particular has a thermal conductivity which in the Comparison with the heat transfer rate due to convection between the wire 12 and the surrounding environment provides an accelerated cooling. More preferably, the heat sink is used 14 to accelerate the cooling rate by at least 25%, and most preferably by at least 100%, compared to the otherwise ambient or heat sink free rate.

Although described herein with particular reference to an SMA, it is within the scope of the invention to take advantage of the disclosure with actuators that utilize other thermally activated active materials, such as those described in US Pat. A shape memory polymer (SMP). The following detailed description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its applications, or uses. As used herein, the term "wire" is not limiting and is intended to encompass other similar geometric configurations that provide tensile strength / elongation, such as cables, bundles, strands, ropes, strips, chains and other elements, to the extent that it is compatible with are compatible with the geometric constraints of the present invention.

As used herein, shape memory alloys (SMAs) generally refer to a group of metallic materials which have the ability to return to a predefined shape or size when subjected to a corresponding thermal stimulus. Shape memory alloys are capable of undergoing phase transformations in which their yield strength, stiffness, dimension, and / or shape are varied as a function of temperature. The term "yield point" refers to the stress at which a material exhibits a well-defined deviation from the proportionality between stress and strain. In general, shape memory alloys can be pseudoplastic deformed in the low temperature or martensite phase and, when exposed to a higher temperature, will convert to an austenite phase or parent phase and return to their shape prior to deformation.

Shape memory alloys exist in several different temperature-dependent phases. The most commonly used of these phases are the so-called martensite and austenite phases, which are discussed above. In the following discussion, the martensite phase generally refers to the more deformable lower temperature phase, whereas the austenite phase generally refers to the more rigid, higher temperature phase. When the shape memory alloy is in the martensite phase and heated, it begins to change to the austenite phase. The temperature at which this phenomenon begins is often referred to as the austenite start temperature (A _s ). The temperature at which this phenomenon ends is often referred to as the austenite finish temperature (A _f ).

When the shape memory alloy is in the austenite phase and is cooled, it begins to change to the martensite phase, and the temperature at which this phenomenon begins is referred to as the martensite start temperature (M _s ). The temperature at which the austenite ceases to convert to martensite is often referred to as the martensite finish temperature (M _f ). In general, the shape memory alloys are softer and more easily deformable in their martensitic phase and harder, stiffer and / or more rigid in the austenitic phase. In view of the foregoing, a suitable activation signal for use with shape memory alloys is a thermal activation signal of a magnitude sufficient to effect transformations between the martensite and austenite phases.

Shape memory alloys may exhibit a one-way shape memory effect, an intrinsic two-directional effect, or an extrinsic shape memory effect in two directions, depending on the alloy composition and processing heretofore. Annealed shape memory alloys typically exhibit only the shape memory effect in one direction. Sufficient heating subsequent to deformation of the shape memory material at low temperature will induce martensite / austenite transformation and the material will recover its original annealed shape. Thus, shape memory effects are observed in one direction only upon heating. Active materials comprising shape memory alloy compositions that exhibit unidirectional memory effects do not automatically reform and are likely to require an external mechanical force to rebuild the shape.

Intrinsic and extrinsic bi-directional shape-memory materials are characterized by a change in shape both when heating the martensite phase and the austenite phase, as well as an additional shape change upon cooling from the austenite phase back to the martensite phase. Active materials that exhibit an intrinsic shape memory effect are made from a shape memory alloy composition that will cause the active materials to self-recover automatically due to the above-noted phase transformations. An intrinsic shape memory behavior in two directions must be induced in the shape memory material by the machining. Such procedures involve extreme deformation of the material while in the martensite phase, heating / cooling under duress or load, or a surface modification by z. As laser annealing, polishing or shot peening. Once the material has been taught to exhibit a shape memory effect in two directions, the strain change between the low and high temperature conditions is generally reversible and is maintained over many thermal cycles. In contrast, active materials that exhibit extrinsic shape memory effects in two directions combine composite or multi-component materials that combine a shape memory alloy composition that exhibits an effect in one direction with another element that provides a restoring force to restore the original shape.

The temperature at which the shape memory alloy reaches its high temperature shape when heated may be adjusted by slight changes in the composition of the alloy and by heat treatment. In nickel-titanium shape memory alloys, it may, for. From above about 100 ° C to below about -100 ° C. The shape recovery process occurs over a range of only a few degrees, and the beginning or end of the transformation can be controlled within one or two degrees, depending on the desired application and alloy composition. The mechanical properties of the shape memory alloy vary widely over the temperature range that spans its transformation and typically impart shape memory effects, superelastic effects, and high damping capability to the system.

Suitable shape memory alloy materials include, without limitation, nickel-titanium based alloys, indium titanium based alloys, nickel aluminum based alloys, nickel gallium based alloys, copper based alloys (eg, copper-zinc alloys, copper Aluminum alloys, copper-gold and copper-tin alloys), gold-cadmium-based alloys, silver-cadmium-based alloys, indium-cadmium-based alloys, manganese-copper-based alloys, iron-platinum alloys Base, iron-palladium-based alloys and the like. The alloys may be binary, ternary, or of any higher order provided that the alloy composition exhibits a shape memory effect, such as a shape memory effect. As a change in the shape orientation, the damping capacity and the like.

In typical use, SMAs exhibit a 2.5 fold modulus increase and a dimensional change (the recovery of pseudoplastic strain induced when in the martensitic phase) of up to 8% (depending on the extent of pre-strain) when heated above their martensite / austenite phase transition temperature.

Coming back to the 1a - 7b is the actuator 10 operable to mechanical work due to a contraction of the wire 12 to perform. The actuator 10 can z. B., as in the 4a - 7b shown, driving technology with a load 16 be coupled. The operating wire 12 is typically with a source 18 however, which may be operable to provide an activation signal thereto, may also be passively activated. If z. B. an ohmic heater is used to the thermal signal through the resistance of the wire 12 to generate, the source can 18 an electrical power supply 18 ( 6 ) such. B. be the charging system of a vehicle. It can be seen that a controller (not shown) is intervening and communicative with the supply 18 and the wire 12 coupled and may be formed to the actuation of the wire 12 and or the timing of the engagement between the heat sink 14 and the wire 12 to control in a selective intervention.

In the 1a - 2 are several cross-sectional configurations of preferred heat sinks 14 shown. In 1a is the sink 14 functional with a variety of wires 12 engaged so as to define a contact engagement surface. More preferably, the sink defines 14 when the item (eg, the wire (s) 12 ) defines a length and width, a contact width greater than the element width, and a contact length of not less than 25%, more preferably not less than 50%, and most preferably not less than 75% of the element length, thus the contact engagement surface define.

The illustrated valley 14 has a massive rectangular main body 20 and a plurality of six "ribs" (or thin, generally vertical, rectangular sections as shown) 22 that comes from the body 20 emerge, and a variety of grooves 24 passing through the body 20 the ribs 22 are defined opposite ( 1a ). The valley 14 is made of a material capable of withstanding the influence of predictable heat energy levels and providing the intended increase in thermal heat transfer rate. This means that the sink material has a thermal conductivity (ie a heat transfer coefficient) which is substantially higher than the normal transmission rates of the ambient space, e.g. B. 0.024 W / mK (the conductivity of air). The valley 14 For example, it may be formed of copper (eg, copper alloys) or aluminum (aluminum alloys), the thermal ones Conductivities of about 400 and 250 W / mK have. At least a portion of the surface of the sink 14 can be polished, roughened or otherwise treated to promote heat transfer.

The grooves 24 show concave formations that are larger than that by the wire (s) by a radius or width of something (eg, preferably 2 to 5%) 12 defined radius or width are defined in the activated state, so that when he / she is arranged therein, the contact engagement surface is increased, and more preferably, so that the wire 12 with the sink 14 generally over the entire surface of the groove 24 in contact. In a preferred embodiment, the through the grooves 24 defined radius further enlarged and the actuator 10 further comprises a thermal grease or other heat transfer interface 26 between the valley 14 and the wire 12 , The preferred interface 26 function to facilitate sliding and allow heat transfer without experiencing intolerable degradation over a high volume of cycles.

It can be seen that the sink 14 from 1a Alternatively it can be turned around and the wires 12 within channels 28 passing through the ribs 22 are defined, can be arranged ( 1b ). Here is a specially designed guide through the sink 14 in every channel 28 be defined as in the first channel 28a from 1b shown so as to increase the contact engagement surface as well as the structural stability; It can turn a thermal paste or interface 26 be provided as in the second channel 28b from 1b shown; or the valley 14 can be made directly on the wires 12 to rest, as in the remaining channels 28 shown. Thus, the sink 14 According to a first aspect of the invention, further comprising a spacer with a rib, which the wires 12 spaced to separate the exhaust tabs and to accelerate the cooling of individual wires.

As in the 1a c, includes the preferred sink 14 an upper and a lower pair fitted together 14ab , which cooperatively function to contact the contact surface by touching the upper and lower halves of the wire (s) 12 to enlarge. In the 1a -C includes the sink 14 z. B. a second identical body 20 with ribs 22 etc. When the wires 12 can define multiple rows (or other configurations), the sink 14 from several sets of matched parts 14a , b, which engage each row or otherwise accommodate the configuration. In 1c were the ribs 22 from the bodies 20 removed so as to facilitate the stacking of the multiple sets and rows. As in the 1a , c, fasteners (eg, screws) may be used 30 be used to the mated parts 14a , b next to the wires 12 to connect with each other and fix fix, so a permanent engagement between the sink 14 and the wires 12 to effect.

In this configuration, the mated grooves define 24 inner channels or spaces in which the wires 12 are held. When disabled, the preferred wires touch 12 the valley 14 minimally ideally along one of the circular cross-sections of each wire 12 and the groove 24 defined tangential line ( 1a , c). Anyone through the valley 14 Heat loss caused during activation is negligible, as it can be seen that SMA actuation is largely adiabatic. If the wire 12 is activated, it expands radially rapidly to fill the space and the contact interface between the wire 12 and the valley 14 essentially to enlarge. This is every wire 12 able to due to the through the sink 14 provided increased thermal heat transfer rate and the enlarged contact engagement surface heat energy at an accelerated rate. It will thus be appreciated that, despite the permanent engagement with each other, minimal heat transfer will occur due to the minimal contact prior to activation; however, there will be an increased heat transfer as soon as the wires 12 are activated.

As in 2 shown, the valley can 14 be a unitary body that holds the wires 12 envelops. The valley 14 can z. B. around the wires 12 be formed around or, if it consists of a foil or the like, at least once around the wires 12 be wrapped around. As in 2 Also shown may be a single rib 22 be oriented horizontally to increase exposure to fluid flow and heat transfer due to convection. In this regard, it can be seen that the sink 14 may be exposed to a specific fluid flow (not shown) which further increases the cooling rate. Ribs 22 can / can z. B. to be brought into engagement with a coolant or a compressed air flow, the / the heat from the surface of the rib / n 22 and again the wires 12 withdraws; or it can, as in 5 shown a variety of coolant holes 23 through the main body 20 defined and fluidly coupled to a coolant source (not shown). In a further aspect of the invention, it will be appreciated that the sink 14 can be used to accelerate heating, z. B. by a heated fluid through the openings 23 is passed through and a selective intervention is effected either before or during the heating or activation periods.

More preferred is the new actuator 10 designed such that the sink 14 and the wire 12 autonomously and autonomously engaging, and further includes a drive mechanism for this purpose 32 , The drive mechanism 32 is driving technology with the sink 14 coupled and operable to its displacement up to a point of contact with the wire 12 to effect. The mechanism 32 is preferably designed to effect such contact without undue stress on the wire 12 apply. The 3a - 7b illustrate exemplary embodiments of selectively engaging wells 14 ,

In 3a is the drive mechanism 32 through the actuating wire 12 itself operated and includes a first and a second curved structure 34 formed of a suitable material. The structures 34 and the wire 12 are generally parallel and have end caps 36 connected with each other. As shown, the structures are inward to the wire 12 Curved, flexible, and designed to stand out from a normal standard configuration in which they use the disabled wire 12 not engaged (in 3a shown in dashed lines) to bend into a more curved configuration when the wire 12 is activated (in 3a shown in solid lines). The structures 34 and the wire 12 are cooperatively configured such that the structures 34 in the more curved configuration, the wire 12 tangentially and then preferably continue to curve to increase the contact-engagement area and to generally absorb any further actuation force transmitted after contact. It can be seen that the structures 34 produce an increasing bias toward the normal configuration as they are caused to curve further, that is, the biasing force acts around the sink 14 after disabling the wire 12 return to the normal configuration, and the biasing force produces a pre-strain within the wire 12 in the deactivated state, which is the reaction of the actuator 10 improved to a subsequent activation.

As in 3b shown, the heat transfer masses (ie the cooling platelets) 38 at the structures 34 fastened along its longitudinal centerlines and adapted to engage with the wire 12 engaged in the activated state to the surface and the heat transfer rate of the sink 14 continue to increase or increase. The preferred platelets 38 define a longitudinal groove (not shown) which, as previously explained, enlarges the contact engagement surface. Again, the structures 34 preferably configured to bend further after contact so as to absorb any residual operating force.

In the 4a -D is shown a self-actuating embodiment in which the drive mechanism 32 a swivel arm 40 includes. The swivel arm 40 is pivotally coupled to a fixed structure near one end to define a pivot axis p, and is drivingly connected to the actuating wire 12 coupled. The swivel arm 40 defines a main and a stretch section 42 . 44 as illustrated. The stretch section 44 extends from the distal or free end of the main section 42 over a predetermined distance relative to the wire length and the intended engagement length. At the end of the stretch section 44 a connecting section expands 46 in the direction of the valley 14 out. The preferred connection section 46 and the valley 14 cooperatively make a universal joint 48 so as to evenly engage between the sink 14 and the wire 12 despite the angular position of the arm 40 to enable.

As illustrated, the wire is 12 with the arm 40 at a point above the pivot axis, and more particularly at one of the available recoverable strain in the wire 12 and the necessary swinging by the arm 40 dependent point connected. More preferably, a fret connects 50 ( 4d ) the wire 12 and the main section 42 of the arm 40 , The Bund 50 has opposite ball joints 52 on that in by the arm 40 formed slots 54 are included. The ball joints 52 and slits 54 allow that arm 40 the linear movement of the wire 12 transformed into a rotational movement. It can be seen that the slot length with those for the arm 40 required degree of vibration is related. Where the covenant 50 stuck with the wire 12 is engaged, it is preferable that the contact between the sink 14 and the wire 12 At the end of the conversion and activation is made, so no excessive tension through the sink 14 on the wire 12 is applied.

In the 4a -D is the mechanism 32 designed to vibrate minimally before coming to the beginning of activation with the wire 12 contact to minimize packaging. As such, the illustrated slots have 54 minimal lengths on ( 4a , d). In this configuration is the federal government 50 in frictional engagement with the wire 12 and preferably includes a solid lubricant 56 disposed internally to allow for initial contact between the sink 14 and the wire 12 a glide takes place and further work through the wire 12 is done ( 4c ). Thus, the necessary frictional force between the solid lubricant 56 and the wire 12 less than the operating force, but greater than the force required to hold the arm 40 to the valley 14 to pivot. More preferably, the lubricant 56 be formed of an additional active material to serve, its adhesiveness and / or on the wire 12 to selectively change the applied shear force.

Once the cooling is complete, the bi-directional shape memory in this configuration can be used to hold the arm 40 to drive back towards normal orientation. It can be seen that here the frictional force is still greater than the force required to hold the arm 40 to pivot in the opposite direction and the sink 14 to raise. Alternatively, a biasing force, for. B. by a torsion spring (not shown), which is aligned coaxially with the pivot axis, or a tension spring 58 ( 4a - 7b ), the drive technology with the arm 40 coupled and trained to the arm 40 be provided back in the direction of normal orientation. It will be appreciated that the frictional force in the latter configuration is greater than the sum of the required moment and preload.

It will be appreciated that alternatively the connecting section 46 instead of or in addition to the frictional engagement between the collar 50 and the wire 12 may have a resistance collapsing configuration. The connecting section 46 can z. B. a telescopic cylinder having a coaxially housed therein compression spring (not shown). Here's the stiffness of the section 46 formed such that the section 46 Collapses before a predetermined undesirable stress on the wire 12 is transmitted.

In 5 is shown a further self-actuating embodiment in which the drive mechanism 32 includes a rack and pinion drive configuration operable to control the horizontal linear action of the wire 12 in a vertical shift of the sink 14 convert. More specifically, in the illustrated embodiment, a horizontal rack 60 with the wire 12 at or near its free distal end by a knee 62 firmly connected so as to maximize the displacement. A first vertical rack 64 is stuck with the sink 14 connected; and a second vertical rack 66 is stuck with a counterweight 68 connected. Each of the racks 60 . 64 . 66 is driving technology with a gear 70 connected, with the vertical racks 64 . 66 opposite in the gear 70 intervention.

The racks 60 . 64 . 66 and the gear 70 are cooperatively designed so that when the wire 12 is activated, the horizontal rack 60 is caused to translate, the gear 70 is made to turn clockwise, the first vertical rack is made to lower, the sink 14 is brought to the wire 12 to engage, and the weight 68 raised at the same time. So by the wire 12 minimizing experienced tension when it is disabled is the counterweight 68 and the valley 14 cooperatively designed to have a negligible positive difference, the difference being equal to the load of the counterweight 68 minus the weight of the sink 14 is. It can be seen that the negligible positive difference is a normally upper (ie disengaged) position for the sink 14 and a pre-strain in the wire 12 if it is disabled, entails; and that through the wire 12 The actuation force produced must overcome only the negligible difference, which allows more force to be used to produce work. It can be seen, however, that when the sink 14 functionally under the wire 12 (in addition to or instead of the illustrated gear / s), the transmission may be mirrored and a negligible negative difference may be present so as to be a normal lower position for the sink 14 to have an effect when the wire 12 is disabled.

In further embodiments, the drive mechanism comprises 32 a separate drive element 72 , which is specially designed for the sink shift. In 6 includes the drive element 72 z. B. at least one auxiliary shape memory alloy wire, the drive technology with a swivel arm 40 is coupled as previously with respect to the 4a -D described. As such, a detailed description of the operation of the arm 40 through the auxiliary wire 72 not repeated here. However, it can be seen that changes to the arm 40 such as B. an extension of the stretch section 44 may be required. Finally, it is certainly within the scope of the invention, more conventional drive elements 72 such as As motors or solenoids or other types of actuators with an active material such. B. electroactive polymer tendons to use the sink 14 drive.

The additional wire 72 can be packed and trained to be in series ( 6 ) or parallel ( 7a , b) or in combinations thereof with the actuating wire 12 to act. When connected in series, the actuator and the auxiliary wires 12 . 72 Be part of a common circuit, so the same source of power and power 18 is used to activate both ( 6 ). In each configuration, the auxiliary wire becomes 72 preferably activated after the actuating wire 12 has been activated, allowing an actuation through the sink 14 is not affected. For a connection z. B. in series, the auxiliary wire 72 be formed of a shape memory alloy having a higher phase transition temperature than that of the actuating wire 12 has a diameter which is larger than that of the actuating wire 12 , or further connected in parallel with additional wires or resistors (not shown).

In the 7a , b is an auxiliary wire 72 with the swivel arm 40 connected and has a parallel configuration relative to the actuating wire 12 on. Again, it is preferred that the actuating wire 12 is fully activated before the auxiliary wire 72 is activated and the wire 12 and the valley 14 be engaged. It will be appreciated that, for this purpose, the sensory technology or resistance analysis of the actuating current may be used to detect complete actuation and activation of the dummy wire 72 trigger only after detection. Alternatively, the actuating and the auxiliary wire 12 . 72 cooperatively be formed such that the auxiliary wire 72 through the from the actuating wire 12 generated heat is activated passively. Finally, be aware that the sink 14 in any embodiment may be designed to engage both the actuating and the auxiliary wire 12 . 72 to be engaged, so as to the heat transfer of both and the availability of the entire actuator 10 to accelerate for subsequent use.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include the same structural elements with insubstantial differences from the literal language of the claims.

Also, the terms "first," "second," and the like, as used herein, do not refer to any order or meaning, but rather are used to distinguish one element from another, and the terms "the "," The "," the "," an "," an "," an "," an "and" an "mean no limitation on the amount, but rather designate the presence of at least one of said element. All ranges that refer to the same amount of a given component or measurement are inclusive of endpoints and can be combined individually.

Claims (10)

A thermally activated actuator having an active material capable of increasing a bandwidth, the actuator comprising: an actuator element made of an active material operable to undergo a reversible change in a fundamental characteristic when exposed to, or shielded from, a thermal activation signal so as to heat and activate or enable the element is cooled or deactivated, wherein the element has an ambient cooling rate when it is shielded from the signal after it has been activated and a first cooling period based on the ambient rate; and a heat sink having a rate of thermal conductivity higher than the ambient rate and automatically engaging the element when the element is activated so as to have a second cooling period shorter than the first period. The actuator of claim 1, wherein the actuator element comprises at least one shape memory alloy wire. The actuator of claim 1, wherein the actuator element causes the drain to independently engage or increase engagement with the actuator element. The actuator of claim 1, further comprising: a separate drive member communicatively coupled to and specifically provided for the drain and configured to cause the sink to independently engage the actuator member. The actuator of claim 4, wherein the drive element comprises an auxiliary active material element operable to undergo a second reversible change in a fundamental characteristic when exposed to or foreclosed to an activation signal to be activated or deactivated , The actuator of claim 5, wherein the auxiliary and actuator members each comprise at least one shape memory alloy wire and the wires are cooperatively configured such that the actuator wire is fully activated before the auxiliary wire is activated. The actuator of claim 1, wherein the element defines a first length and width and the valley has a second width greater than the first width and a second length not less than 25% of the first length. The actuator of claim 1, wherein the member and the well define a contact engagement surface, the member comprises at least one shape memory alloy wire, and the well defines at least one groove or channel that is formed to increase the contact engagement surface. The actuator of claim 1, wherein the sink defines a surface that is exposed to ambient conditions and has at least one rib that is configured to increase the surface area. The actuator of claim 1, wherein the drain defines at least one fluid port.

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